Summary A. DNA Ligase III. DNA Ligase is a specific type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. It plays a role in repairing single-strand breaks in duplex DNA in living organisms. This protein has been investigated in different cells by SDS-PAGE coupled to mass spectrometric analyses. B. Telomerase. Telomerase is a ribonucleoprotein that is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands. Induction of this protein was investigated by SDS-PAGE coupled to mass spectrometric analyses. C. Pulegone. Pulegone is a commonly-used flavoring agent (mint flavoring) and is known to be toxic in high doses. Using microscopy, it has been shown that glomerulopathy can occur when rats are given high doses of this chemical. To address the composition of the kidney of affected rats, we are using mass spectrometry to identify the proteins present as well as determine which proteins are affected by this chemical. This study should provide a significant amount of information that can help in understanding the mechanism of this chemical.